In one form of conventional chain saw, the chain carrying the cutting elements moves about a forwardly extending bar. The bar is cantilevered from a power drive which may comprise an engine or an electric motor, as desired. The power drive conventionally includes an outer housing having one or more handles for manipulating the chain saw in the use thereof.
A problem arises when such a chain saw is utilized to initiate a cut through a wall surface, and the like. Such use is often required by firemen and the like, such as for cutting through a roof in order to gain access to or ventilation of the subjacent space.
In using the conventional chain saw for this purpose, the operator must attempt to urge the chain at the distal end of the bar downwardly through the roof surface portion. Such use of the chain saw is dangerous in that the chain may slip on the roof surface or tend to walk about prior to gaining purchase in the roof.
Further, existing chain sawing equipment does not lend itself to safe operation when used to cut through roofs and the like. Existing roof structures may be sloped up to 45.degree.. A fireman must put himself often in an unsafe and awkward position on such sloping surfaces to stabilize himself. In addition, existing power saws cannot be set on the roof to facilitate their use in gaining access. They must be held in dangerously awkward positions in order to complete the task properly.
Resort has been had to initiating a cut through such a roof surface by means of an axe or similar initial penetrating tool. When the opening in the roof thusly formed is of sufficient size to pass the bar-carried chain downwardly therethrough, the user may then use the chain saw in the normal manner in effecting an enlargement of the opening. The axe is often used to make the entire vent hole. This method is time-consuming and the time the fireman must spend on the roof of a burning structure presents a serious safety problem.
Such a procedure has the serious disadvantages of requiring a plurality of different tools and is relatively slow in effecting the desired entrance opening.